Piston



Sept 156, 2924. was-5M A. TAUB PISTON Filed March 8, 1922 Patented Sept, 16, 1924..

UNITED .sra'rss ra ranr eer e-a.

ALEX TAUB, or DETROIT, MICHIGAN, ASSIGNOR To GENERAL MOTORS oonnomrrrow, or DETROIT, MICHIGAN, A CORPORATION OF DELAWARE.

PISTON Application filed March 8, 1922. Serial No. 542,038.

To all whom it may concern:

Be it known that I, ALEX TAUB, a citizen of the United States, and a resident of Detroit, county of Wayne, and State of Michigan, have invented certain new and useful Improvements in Pistons, of which the following is a full, clear, concise, and exact description, such as will enable others skilled in the art to which the invention relates to make and use the same, reference being made therein to the accompanying drawings,

which form apart of this specification.

The invention relates to pistons and more particularly to those of the type generally employed in connection with internal combustiori'engi'nes;

The principalobject or theinvention is to provide apiston of soft metal, such as aluminum or one of its alloys, having different portions thereof capable of being formed integrally, as by casting, but of differing hardness. Y

It is common practice to utilize for the pistons of internal" combustion engines a metal or alloy which is softer than the material of the cylinder. walls, thereby reducing the wearof the cylinder to a minimumand preventingscoring of the walls. Since cast iron is commonly employed for the cylinders, from a metal softerthan castiron, alumi num or one of its alloys being well recognized as suitable for that purpose because of its softness and other advantageous prop-- .erties, including lightness.-

Contact with the cylinder walls, however, occurs chiefly in the guide or skirt portion of the-piston, in which region relative soft ness is of advantage as mentioned above,

whereas in the head portions-of the piston and the region constituting a bearing for the wrist pin, a greater degree-of hardness is desirable in order toavoid excessivewe'ar 1n the pin bearings and piston ring grooves;

With the object therefore of producing a piston having a relatively soft skirt portion and a relatively hard head portion, at the same time retaining the advantages in sim- I p tya struction due to the formation of the piston strength and cheapness of conin one piece, I propose to subject the piston to a treatment especially desi ed to develop different degrees of her ness'in different portions thereof. I

ile various methods may be employed it is usual to form such pistons t'oefl'ect a variation in hardness between the head and skirt portions of the piston, I prefer to utilize a differential heat treatment and will describe herein. a treatment whigh may be readily applied during the casting of the piston. In accordance with this method, portions of the mold to be used in casting the piston may be formed of materials adapted to conduct heat rapidly from the surface of the molten metal, thereby chilling the metal which ing the hardness in the chilled sections of thecast article. 7

vThe results, as well as one form of apparatus in which the operation may be carried out, are illustrated in the accompanying drawings, inv which Fig; '1 is. an elevationpartly in cross-section representing a piston embodying the invention; and

Fig.v 2 is a cross-section representing a mold with a piston as. cast therein.

Referring to the drawings, resented in Fig. 1 includes a contacts with such "port ons of the mold and materially increasthe piston rep head portion ,5-

and Skirt portion 6. Grooves 7, which may be formed in the process of casting, are pro vided in the headpo rtion-'.of the piston to '4 receive the usual packing rings. Bearings '8, positioned intermediate the, head and skirt portions, provide a means of support for the piston pinwhereby the connecting rod maybe attached to the piston. The

jheadportion of. the piston extending to a proximately the plane of the axis of t e piston pin bearings is hardened as indicated by the cross-hatching in order to resist wear.

other material having good heat conducting.

properties, while the upper portion 13 is of non-conducting material, such for example,

as ordinary melding sand. e inner mold member 11 is also of non-conducting material. The core A for the piston pin bearings should also be of conducting material, as iron, in order to provide -a chill for the bear ing surfaces.

The cooling of the head portion of the piston may be facilitated by providing a hollow space within the portions 12, 12', of the mold, in which space a cooling fluid, as steam, may be caused to circulate, suitable supply and outlet passages being provided as indicated at 16, 17, respectively.

In casting pistons in apparatus such as described, it will be understood that the portions which are cast in contact with the conductingsurfaces of the parts 12, 12', 14, will be chilled and thereby rendered'harder than the portions which are cast in contact with the non-conducting materials. In accordance with this process it has been foundpossible to produce an alloy piston the skirt portion of which has a hardness, as represented on the Brinell scale, of 85 to 95, while the head portion has a hardness of 125 to 140.

It will be understood that the details of structure and operation may be varied widely without departing from the spirit and scope of the invention, and therefore I do not wish to be limited to the'specific details above set forth except as required by Leoaeer the language of the appended claims in view of the prior art.

2. A piston formed in one piece from metal comprising chiefly aluminum, "the head portion of the piston being harder tha the skirt portion. 1

' 3. A." piston metal softer thancast iron and having the portions adjacent to the piston ring grooves hardened to resist wear, the skirt portion being softer than the saidhardened portion.

4. A piston formed in one piece from metal softer than cast ironand having the portions adjacent to the piston ring grooves and to the piston pin bearings hardened to resist wear, the skirt portion being softer than the said hardened portion.

5. A cast metal pistonformed in a single piece from metal comprising chiefly aluminum, the portions adjacent to the head, ring grooves and pin bearings being chilled to resist wear and the skirt portion being softer than the said chilled portions.

In testimony whereof I afiix my signature.

ALEX 'IAUB.

formed inv one piece from' SID 

